Electrical switches using push button or plunger type switch actuators have many applications including use in automobile car doors, ignition circuits, power take-offs for lawn mowers and the like. These push buttons may be normally open, normally closed or a combination of the two.
It is possible to construct switches having more than two terminals which combine the features of normally open and normally closed switches. For example, a “double-pole double-throw” switch behaves as a normally open switch and a normally closed switch in parallel operated by a single plunger. When the plunger is in a normal position, one pair of normally closed terminals is bridged and a pair of normally open terminals is isolated. Alternatively, when the plunger is moved to an actuated position, the normally open terminals are bridged and the normally closed terminals are isolated. A “single-pole double-throw” switch behaves like a double-pole double-throw switch in which one of the normally open terminals is coupled to one of the normally closed terminals. When the plunger is in the normal position, a common terminal is bridged with a normally closed terminal while a normally open terminal is isolated. Alternatively, when the plunger is in the actuated position, the common terminal is bridged with the normally open terminal while the normally closed terminal is isolated.
Several proposals have been made with respect to switches in which torsion springs, leaf springs or “V”-springs are carried by plungers and used to bridge gaps between spaced terminals when the plungers are appropriately positioned. Such springs must be secured to the plungers so that the springs do not pull loose as the plungers move them into or away from engagement with the terminals. One such proposal uses a wire torsion spring having a central coil mounted on a post projecting from a surface of the plunger. An advantage of this mounting technique is that the spring may be coupled to the plunger without resort to grease to hold the parts together during assembly prior to welding. A drawback to this technique is that forming the loop which engages the post increases the cost of the spring.
U.S. Pat. No. 5,528,007 to Williams (incorporated herein by reference) concerns a plunger switch having a plunger, a retainer, a pair of terminals and an electrically-conducting wiper contact having a curved or bent middle portion defining two oppositely directed legs on either side of the middle portion. The retainer cooperates with the plunger to carry the wiper contact as the plunger moves between a normal and an actuated position. The terminals have facing contact surfaces for biased engagement with the portions of the legs exposed by the plunger and retainer to form an electrical path between the terminals when the plunger is in the actuated position. The plunger and the retainer are coupled together by arms which project from either the plunger or the retainer. The wiper contact is secured between the plunger and retainer without the need for forming a central loop in the wiper contact for engagement by the plunger.